The surface coating of superabrasives

The surface coating of superabrasives is to use surface treatment technology to coat the surface of superabrasives particles with films of other materials. superabrasivess with different coatings on the surface have become a new variety with different properties. Synthesis, sorting, coating and sintering (polycrystalline manufacturing) are the four main ways for the multi variety development of superabrasivess.

The coated superabrasives usually refers to superabrasives particles of various sizes. As a coating material, it is usually metal (including alloy), such as copper, nickel, titanium, molybdenum, copper tin titanium alloy, cobalt plated alloy, cobalt phosphorus alloy, etc; Some coating materials are also non-metallic materials, such as refractory hard materials such as ceramics, titanium carbide, titanium nitride and other compounds. When the coating material is metal, the coating on the surface of superabrasives can be called metal coating, or commonly known as metal coating, or surface metallization.

The purpose of surface coating is to endow superabrasives particles with special physical and chemical properties, so as to improve their use effect. For example, the service life of resin grinding wheel made of coated diamond or cubic boron nitride can be extended by 50% - 100% or more.

Classification of surface coating methods

Industrial surface treatment methods include wet method and dry method.
Among them, the methods that have been actually applied to the coating of superhard abrasive surfaces are mainly chemical coating (without electrolytic coating) and electrocoating in wet coating, chemical vapor precipitation (CVD) and physical vapor precipitation (PVD) in dry coating (also called vacuum degree), including vacuum powder metallurgy liquid phase sintering, which have been applied in practice.

Effect of metal coating on the surface of superhard abrasive

(1) Improve the bonding strength between the diamond abrasive powder and the bonding agent of the abrasive tool, and the coating acts as a bonding bridge between them.
(2) Reduce heat shock. The metal coating conducts heat more slowly than the superhard abrasive. The grinding heat is transferred to the resin bond at the contact with the abrasive after being buffered by the coating to prevent it from being burnt by the impact of the instantaneous high temperature, thus maintaining its grip on the abrasive.
(3) Improve the particle strength of the abrasive. The coating plays the role of reinforcement and toughening. The buffer effect caused by the thickness of electroless coating and electrocoating makes the strength of low, medium and high series products increase by 50% - 100%, 50% - 60% and 30% respectively.
(4) Thermal insulation protection. During high temperature sintering and grinding, the coating can isolate and protect the diamond from rock desertification, oxidation or other chemical changes.